Security forces are reportedly checking documents and questioning people in the capital about the attacks. School holidays have been extended until next week due to security considerations. The country's borders are also being tightly controlled.
Meanwhile, Tashkent was the scene of another incident today. Police say a man blew himself up after a standoff with security forces. Police denied earlier reports that he had taken hostages.
A correspondent from RFE/RL's Uzbek Service spoke to a police officer, who declined to identify himself: "[The suspect] was by himself. There were no hostages. The reason [the operation] took so long was that we had to check if there were any bombs, mines, etc. Everything was fine. Neighbors [who were evacuated] are going to be back [in their homes]."
The incident brings to at least 43 the number of people reported killed since a wave of bombings and clashes began 28 February in the central Uzbek city of Bukhara.
No group has claimed responsibility for the attacks. Authorities are blaming Islamic militants.
Ilya Pyagay, the deputy antiterrorism chief for the Uzbek Interior Ministry, said today the violence is connected to Al-Qaeda. Uzbek officials had earlier blamed Hizb ut-Tahrir, an Islamic group seeking the creation of a caliphate spanning all of Central Asia.
Hizb ut-Tahrir, which has no known links to extremist violence, has denied any involvement.
A special government commission headed by Uzbek President Islam Karimov is investigating the attacks.
U.S. State Department spokesman Adam Ereli yesterday reaffirmed Washington's support in helping Tashkent find those responsible.
"I think it's clear that, based on the horrific attacks that Uzbekistan has suffered in the past few days, that it, like the rest of us, is a target of terrorist action. They are taking, I think, aggressive response to those attacks. We will support them in providing them whatever assistance they need to combat the terrorist threat that they face," Ereli said.
Human rights activists say they fear Uzbek authorities may use the crackdown to repress members of the country's religious communities and legitimate political opposition groups.
Aaron Rhodes is the director of the International Helsinki Federation for Human Rights in Vienna.
"Our organization condemns these terrorist attacks. And we urge the Uzbek security authorities to be careful not to violate the rights of any citizens in their attempts to protect the population from terrorism and especially to avoid [persecuting] Islamic believers who are not members of registered mosques and schools. These are the people who have very typically been the victims in Uzbekistan of unwarranted imprisonment and of torture and even extra-judicial executions in some cases," Rhodes said.
The Uzbek government alleges links between Hizb ut-Tahrir and the militant Islamic Movement of Uzbekistan (IMU). The IMU was set up with the goal of overthrowing Karimov's government and is listed by the U.S. State Department as a terrorist organization. Authorities accused the group of being behind a series of bombings in Tashkent in 1999.
Critics say blaming Hizb ut-Tahrir suits the political agenda of President Islam Karimov. A new report by the New York-based Human Rights Watch accuses the Uzbek government of arresting and torturing thousands of Muslims who practice their faith outside strict state controls.
(RFE/RL's Uzbek Service contributed to this report.)